Chemokines are chemotactic cytokines that are released by a wide variety of cells to attract macrophages, T cells, eosinophils, basophils and neutrophils to sites of inflammation (reviewed in Schall, Cytokine, 3:165-183 (1991), Schall, et al., Curr. Opin. Immunol. 6:865-873 (1994) and Murphy, Rev. Immun., 12:593-633 (1994)). In addition to stimulating chemotaxis, other changes can be selectively induced by chemokines in responsive cells, including changes in cell shape, transient rises in the concentration of intracellular free calcium ions ([Ca2+]), granule exocytosis, integrin upregulation, formation of bioactive lipids (e.g., leukotrienes) and respiratory burst, associated with leukocyte activation. Thus, the chemokines are early triggers of the inflammatory response, causing inflammatory mediator release, chemotaxis and extravasation to sites of infection or inflammation.
There are two main classes of chemokines, CXC (alpha) and CC (beta), depending on whether the first two cysteines are separated by a single amino acid (C—X—C) or are adjacent (C—C). The alpha-chemokines, such as interleukin-8 (IL-8), neutrophil-activating protein-2 (NAP-2) and melanoma growth stimulatory activity protein (MGSA) are chemotactic primarily for neutrophils, whereas beta-chemokines, such as RANTES, MIP-1a, MIP-1b, monocyte chemotactic protein-1 (MCP-1), MCP-2, MCP-3 and eotaxin are chemotactic for macrophages, T-cells, eosinophils and basophils (Deng, et al., Nature, 381:661-666 (1996)). The chemokines bind specific cell-surface receptors belonging to the family of G-protein-coupled seven-transmembrane-domain proteins (reviewed in Horuk, Trends Pharm. Sci., 15:159-165 (1994)) which are termed “chemokine receptors.”
On binding their cognate ligands, chemokine receptors transduce an intracellular signal though the associated trimeric G protein, resulting in a rapid increase in intracellular calcium concentration. There are at least eleven human chemokine receptors that bind or respond to beta-chemokines and at least seven human chemokine receptors that bind to the alpha chemokines. Additionally CX3CR1 (fractalkine receptor) can bind to the fractalkine chemokine, which is distinguished by a series of three amino acids between the first two cysteines. Chemokine receptors, have been implicated as being important mediators of inflammatory and immunoregulatory disorders and diseases, including asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and atherosclerosis.
The CC Chemokine receptor 4, CCR(4), first identified by Power et al. (Power et al. (1995) J. Biol. Chem. 270:19495-19500), is a G protein-coupled receptor that binds to chemokines including CCL22, also known as Macrophage-Derived Chemokine (MDC; a CC chemokine reported to be a chemoattractant for the Th2 subset of peripheral blood T cells, dendritic cells, and natural killer (NK) cells), and CCL17, also known as TARC (thymus and activation-regulated chemokine), which is also produced by monocytes and dendritic cells.
The full-length human CCR(4) protein (GenBank Accession No. X85740; SWISS-PROT Accession No. P51679) has been described, see, e.g, Imai et al. (1998) J. Biol. Chem. 273:1764-1768.
While the global distribution of CCR(4) is unknown, the receptor is expressed primarily in peripheral blood T lymphocytes, and is found on approximately 20% of adult peripheral blood effector/memory CD4+ T cells. CCR(4) is involved in T lymphocyte homing to the skin and lungs (see, e.g., Campbell et al. (1999) Nature 400:776-780, Gonzalo et al. (1999) J. Immunol. 163:403-5 411, Lloyd et al. (2000) J. Exp. Med. 191:265-273, Kawasaki et al. (2001) J. Immunol. 166:2055-2062) and is found on almost all T cells that have a skin homing phenotype, the CTLA+ T cells. Thus CCR(4) may be an important player in skin pathologies in which leukocytes participate. It also seems likely that CCR(4) is expressed on some other cell types, probably monocytes/macrophages and dendritic cells, among others. In view of the clinical importance of CCR(4), the identification of compounds that modulate CCR(4) function represent an attractive avenue into the development of new therapeutic agents. Such compounds and methods for their use are provided herein.